This invention relates generally to interval timer systems and more particularly to a system employing oscilloscope trigger and sweep circuitry to automatically measure time intervals between events in an input signal.
Operators often use an oscilloscope to measure a time interval between events in an input signal. An "event" is usually a point at which the input signal reaches a particular magnitude. For example, the period of a sine wave signal can be determined by measuring the interval between zero crossings. The rise time of a square wave signal can be determined according to the interval between 10% and 90% of its peak level. Traditionally such measurements are made utilizing display of a waveform representation of the input signal on an oscilloscope screen. An operator determines the interval between the two events through measurement of the horizontal distance between the two events on the oscilloscope screen in units of "horizontal divisions" of a rectangular grid system superimposed over the waveform display. The operator then multiples the distance by the sweep rate of the oscilloscope expressed in units of time/division to obtain the time interval. This time interval measurement method is not only slow but is often relatively inaccurate because the operator is unable to gauge distances properly.